Tobacco curing process and apparatus for implementing the process

ABSTRACT

A tobacco curing process including the steps of advancing the tobacco in strip form within a rotary cylinder, spraying the strips with an atomized mixture of substances able to improve the tobacco characteristics, spraying with a steam jet, during the curing treatment, discrete zones of the inner lateral surface of said cylinder, thus exercising a mechanical scraping action.

FIELD OF INVENTION

This invention relates to a tobacco curing process and an apparatus forimplementing the process.

BACKGROUND OF INVENTION

Tobacco processing includes a treatment known as "curing" by which thetobacco is treated with a solution based on sugar, liquorice andquantities of mineral salts.

This treatment, the purpose of which is to improve the tobaccocharacteristics, is generally effected using a rotary cylindercontaining the tobacco in the form of leaf pieces (strips) which aresprayed with this solution heated to 70°-80° C. and atomized with steam.

The particular temperature conditions and the type of substances usedmeans that during curing, a part of the tobacco leaves compressestogether to the cylinder walls, with consequent loss of tobacco leaves.

In the subsequent drying stage, that part of the compressed leaves whichseparates from the cylinder cannot be dried effectively, so that thereis a further loss of tobacco.

To obviate this drawback it has been proposed to use a rotating brushwhich slides against the inner walls of the cylinder, however thissolution has further drawbacks, and in particular:

a loss of time at the end of the process for cleaning the brush, towhich the compressed strips remain attached, and

a considerable loss of strips.

DISCUSSION OF THE PRIOR ART

DE-A-3001734 describes a rotary drum provided with an axially arrangedsteam pipe that is provided with a number of holes bored in the wall ofthe pipe. Steam is ejected from these holes and is directed upwardlyagainst the inner wall of the drum to remove any tobacco particles whichmay adhere to this inner wall.

EP-A-0273596 discloses a method for treating particulate material with aliquid additive in a rotatable cylinder involving the use of apressurized fluid such as steam directed obliquely against the innerwall of the cylinder via nozzles to effect a cleaning action on theinner wall.

SUMMARY OF THE INVENTION

An object of the invention is to provide a process which enables theinner walls of the cylinder to be maintained constantly clean withoutincreasing the operating cost or the loss of tobacco leaves.

This object and further ones which will result from the followingdescription are attained according to the invention through a tobaccocuring process comprising the steps of:

a) advancing the tobacco in strip form within a rotary cylinder,

b) spraying said strips with an atomized mixture of substances able toimprove the tobacco characteristics,

c) spraying with a steam jet through reciprocating motion along thelongitudinal axis of said rotary cylinder, during the curing treatment,discrete zones of the inner lateral surface of said cylinder, thusexercising a mechanical scraping action.

To implement the process the invention uses an apparatus comprising arotary cylinder provided with a feed opening for tobacco strips and adischarge hopper, said cylinder housing a pipe feedable with steam, saidpipe being arranged parallel to the cylinder axis and being providedwith a plurality of spray nozzles facing the surface of said cylinderwherein said pipe is axially movable.

BRIEF DESCRIPTION OF THE DRAWING

A preferred embodiment of the present invention is described hereinafterwith reference to the accompanying drawing, which represents a schematicside view of an apparatus for implementing the process of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As can be seen from the drawing, the tobacco curing process according tothe invention uses a rotary cylinder 1 arranged slightly inclined, itbeing open at the feed end for the tobacco leaf pieces (strips) andclosed at its other end by a discharge hopper 2.

The discharge hopper 2 is provided with a centrifugal fan 3 able tocreate a slight vacuum within the rotary cylinder 1.

The cylinder 1 is provided at its entry opening with an annular flange 4on which there is mounted a bracket 5 provided with slide guides for apipe 6 arranged parallel to the axis of the cylinder substantially atits lateral surface, and provided with a plurality of spray nozzles 7facing said surface.

The pipe 6 is fed with steam from a boiler 8.

Externally to the cylinder at the opposite end to the bracket there ismounted a further bracket for supporting a hydraulic cylinder-pistonunit 9, to the rod 10 of which there is pivoted a bar 11 having itsother end pivoted to the pipe 6. The bar 11 is also pivoted in itscentre to an arm 12.

The apparatus also comprises a spray device, indicated overall by 13 andconsisting of a tank 14 for a mixture suitable for the curing treatment,a pipe 15 with a feed pump 16, and a spray nozzle 17 facing the interiorof the cylinder.

With the process of the invention the tobacco strips conveyed along afeed belt 18 are introduced into the rotary cylinder 1 and are treatedwith the curing mixture delivered via the atomizer nozzle 17.

Steam is simultaneously fed, to emerge from the spray nozzles 7 andexerts a mechanical scraping action on the walls of the cylinder 1, sopreventing formation of tobacco leaf accumulations.

During this stage the rod 10 is moved reciprocatingly, with consequentaxial movement of the pipe 6 in both directions. In this manner,virtually total cleaning of the cylinder can be achieved with a minimumquantity of steam.

I claim:
 1. A tobacco curing process comprising the steps of:a)advancing the tobacco in strip form within a rotary cylinder, b)spraying said strips with an atomized mixture of substances able toimprove the tobacco characteristics, c) spraying with a steam jet,during curing treatment, discrete zones of the inner lateral surface ofsaid cylinder, thus exercising a mechanical scraping actioncharacterized by spraying said steam jet with a reciprocating motionalong the longitudinal axis of said rotary cylinder.
 2. A process asclaimed in claim 1, wherein said spraying step is done on the innerlateral surface of the cylinder in its upper region.
 3. An apparatus asrecited in claim 4, wherein said pipe is axially movable under controlof a level operated by a hydraulic cylinder-piston unit.
 4. An apparatusfor curing tobacco comprising:a rotary cylinder having a feed openingfor tobacco strips, a discharge hopper, said rotary cylinder housing apipe, having a flow of steam therein, said pipe being arranged parallelto an axis of said rotary cylinder and being provided with a pluralityof spraying nozzles facing a surface of said cylinder to spray saidstrips with an atomized mixture of substances able to improve thetobacco characteristics, wherein a steam jet is sprayed onto discretezones of an inner lateral surface of the rotary cylinder in areciprocating motion along a longitudinal axis of said rotary cylinderby moving said pipe axially.